title: Carrier mediated uptake of dehydroascorbate into higher plant plasma membrane vesicles shows trans-stimulation.
abstract: The activity of the ascorbate (Asc) carrier of purified Phaseolus plasma membranes is demonstrated to be highly stimulated when membrane vesicles are preloaded with Asc. Asc transport is inhibited by DTT but is not affected by glutathione or ferricyanide, indicating that dehydroascorbate (DHA) is the preferred species for uptake. Asc transport in the loaded vesicles showed saturable kinetics with an apparent affinity constant of 24 microM and maximal uptake rate of 94 pmol/mg/min. Addition of DHA stimulated the efflux of Asc molecules from the loaded vesicles. Together these results suggest the presence of an Asc/DHA exchange mechanism in higher plant plasma membranes.
authors.affiliation: Department of Biology, University of Antwerp (RUCA), Belgium. neho@ruca.ua.ac.be
authors.forename: N
authors.initials: N
authors.lastname: Horemans
authors.forename: H
authors.initials: H
authors.lastname: Asard
authors.forename: R J
authors.initials: RJ
authors.lastname: Caubergs
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003683:Dehydroascorbic Acid / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D007887:Fabaceae / Q000378:metabolism*; D005292:Ferricyanides / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology; D018546:Hypocotyl; D007700:Kinetics; D010946:Plants, Medicinal
chemical_list: D002352:Carrier Proteins; D005292:Ferricyanides; C007931:hexacyanoferrate III; D005978:Glutathione; D004229:Dithiothreitol; D003683:Dehydroascorbic Acid